This application claims the priority of Korean Patent Application No. 2002-71610, filed on Nov. 18, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an optical recording medium and a method of manufacturing the same, and more particularly, to an optical recording medium using a phase transition layer and a method of manufacturing the optical recording medium.
2. Description of the Related Art
In conventional optical recording media such as compact disks (CDs) or digital versatile disks (DVDs), a phase transition layer is deposited on a substrate, pits are formed on a specific spot by melting and cooling the specific spot by projecting laser beams thereinto, and data is recorded in the pits. Conventional optical recording media adopting this recording method have a technical limit in increasing the numerical aperture of a lens that focuses laser beams. Thus, conventional optical recording media also has a limit in increasing the recording density.
To solve these problems, U.S. Pat. No. 6,197,399 discloses a recording medium that can achieve recording without using laser beams and a method of manufacturing the recording medium.
FIG. 1 is a cross-section of the recording medium disclosed in U.S. Pat. No. 6,197,399. First, a silicon substrate 21 with a 3-inch size and a 1.22 mm thickness undergoes a hydrochloric acid treatment to remove a natural oxide film from the silicon substrate 12, resulting in hydrogen atoms on the surface of the silicon substrate 21. Electron beams are projected into the resulting silicon substrate 21 so that a plurality of circular areas of 10 nm size each are regularly arranged at intervals of 30 nm thereon. Thereafter, the resulting silicon substrate 21 is left in an air atmosphere of a clean room for about an hour, and SiO2 films are selectively formed on areas of the silicon substrate 21 that are exposed to the electron beams. Then, the resulting silicon substrate 21 undergoes another hydrochloric acid treatment to remove some of the SiO2 films from the silicon substrate 21. As a result, pits with a 10 nm width and a 5 nm depth each are formed.
Doner organic dye molecules are vacuum-deposited on the upper surface of the resulting silicon substrate 21 to obtain a recording layer. Then, the resulting silicon substrate 21 having the recording layer formed thereon is heated about an hour at 80° C. in a nitrogen atmosphere. The resulting silicon substrate 21 is polished using 100 nm-sized silica particles at a room temperature to make the organic dye molecules to remain in selected pits, thereby forming recording domains 26. Thereafter, the resulting silicon substrate 21 is left to stand for about a day at 40° C. in an air atmosphere to form a SiO2 film 24 on areas of the silicon substrate 21 that are not exposed to electron beams. A protection layer 27 is formed on the upper surface of the SiO2 film by spin-coating the SiO2 film with a compound composed of polyaniline and polyvinyl chloride. In this way, a recording medium is manufactured, and recording is performed by injecting positive charges (holes) into the dot-like recording domains by means of an atomic force microscope (AFM) probe coated with Au under an applied voltage of 30V.
In the manufacture of the recording medium disclosed in the above U.S. Patent, since a phase transition material, such as doner organic dye molecules, is formed by a hole filling operation, a process of removing the phase transition material from the silicon substrate must be performed after the hole filling operation, and a SiO2 film, in which holes are formed, cannot be removed. Also, a process of heating the phase transition layer is required, and a substrate must only be formed of a material with a high melting point, such as, silicon or special glass.